Materials Literature
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Abstract The effect of zinc catalysts on the hydrolytic depolymerization of polyethylene terephthalate (PET) melts in excess water was studied using a 2‐L stirred pressure reactor at temperatures of 250, 265, and 280°C. The main products of the reaction were found to be terephthalic acid, ethylene glycol, and diethyle…
Computer simulations and experimental studies were combined to design copolymers that enhance the strength of polymer composites. These copolymers contain side chains that associate across the boundary between phase-separated regions to form a "molecular velcro" that effectively binds the regions together. This behavi…
The scaling of the cubic nonlinearity gamma with chain length in polyenic molecules has received considerable theoretical attention. Earlier experimental investigations have been restricted to oligomers with fewer than 20 double bonds because of problems associated with the synthesis and solubility of conjugated molec…
Clusters of metal ions are a class of compounds actively investigated for their magnetic properties, which should gradually change from those of simple paramagnets to those of bulk magnets. However, their interest lies in a number of different disciplines: chemistry, which seeks new synthetic strategies to make larger…
Bis zur vierten Generation sind neutrale, phosphorhaltige Dendrimere auf dem hier beschriebenen Weg in guten Ausbeuten zugänglich. Als einzige Nebenprodukte entstehen NaCl und H 2 O, und die Produkte enthalten hochreaktive Funktionalitäten an der Peripherie. Rechts ist das Dendrimer der ersten Generation gezeigt. magn…
In einer simplen Eintopfreaktion sind die Wirt‐Gast‐Verbindungen 1 (weiße Kugeln=Fe III , schwarze = Fe II , graue = NH , abgewinkelte Stäbe= 2 ) in Gramm‐Mengen durch Selbstorganisation zugänglich. Sie sind die einzigen vollständig charakterisierten Redoxisomere, deren Cyclovoltammogramme vier quasireversible Wellen…
Flüssigkristallines Verhalten über einen weiten Temperaturbereich und reversible Phasenübergänge zeigt das Polymernetzwerk 1 , das durch Wasserstoffbrückenbindungen zwischen den Benzoesäure‐ und den Bipyridyleinheiten zusammengehalten wird. magnified image
Abstract Die Rolle von Metalloenzymen in wichtigen biologischen Prozessen hat in den letzten Jahrzehnten zunehmend Beachtung gefunden. Von den vielen chemischen Reaktionen, die durch Enzyme gesteuert werden, sind nur wenige eine so große Herausforderung wie die Mehrelektronen‐Redoxreaktionen. In neueren Untersuchungen…
Investigations of the infrared and polarized Raman spectra of Cd(HCOO)2 · 2 H2O reveal the presence of two crystallographically nonequivalent formate ions as separate frequencies are observed for each internal mode. The symmetric CO2 stretching mode is observed in between the two components of the in-plane OCH bending…
Les propriétés optiques d'une série d'oxydes mixtes du systeme BaO-RE2O3 (RE = Gd, Y), de formule générate BaRE2O4 sont analysées. L'europium trivalent est utilisé comme dopant actif, remplaçant en partie l'élément de terre rare de la matrice. La quantité du dopant est faibic (2%) et n'altßre pas la structure. D'après…
The Raman spectra of Bi2Ti4O11 at hydrostatic pressure or high temperature show that the frequency of the soft mode has a non-zero value at the phase transition point. The Raman spectra of Bi1.8La0.2Ti4O11 and Bi1.8Yb0.2Ti4O11 at high pressure reveal that there is an additional phonon mode in the low-frequency region.…
The temperature behavior of the charge-density-wave (CDW) state in one-dimensional conductors is studied within the framework of a mean-field approach using the exact solution of the self-consistent equations. The properties of the CDW condensate are found to be dependent on the value of the dimensionless parameter wh…
The specific heat of Grafoil, an artificial graphite made by Union Carbide, has been measured at temperatures as low as 100 mK, thus extending substantially the range investigated up to the present. An unusual contribution to the specific heat is found which obeys a ${\mathit{T}}^{\mathrm{\ensuremath{\alpha}}}$ law (w…
The unusual galvanomagnetic properties of the monoclinic semimetal ${\mathrm{SrAs}}_{3}$, first-order longitudinal Hall effect and magnetoresistivity in Hall geometry, are quantitatively described within a two-band model. The ten model parameters for T\ensuremath{\rightarrow}0 K are obtained from a fit to 14 low-field…
The current through porous silicon p-n junctions is measured as a function of bias voltage and temperature. The ideality factor m=4 value observed under forward bias indicates that channels are present at the unpassivated porous silicon junction surfaces. The generation-recombination current stemming from the space-ch…
A simple two-variable model for the dynamics of sheared colloidal crystals gives shear-melting at low shear rates and suggests a novel mechanism for recrystallization to the solid phase at high shear rates. The nonequilibrium phase diagram agrees qualitatively with experiments and molecular dynamics simulations.
By taking together various observations on air bubbles bursting at the surface of seawater, the production rate and size spectrum of film drops are deduced. The number of film drops produced is proportional to the square of bubble diameter, and the size spectrum of film drops produced by bubbles of various diameters i…
We report on structural and electrical properties of thin granular ${\mathrm{Pd}}_{\mathit{x}}$${\mathrm{C}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ films with palladium (Pd) metal volume fractions 0.3x0.34, approaching the percolation threshold (${\mathit{x}}_{\mathit{p}}$=0.3) from the metallic side. As revealed from…
In small samples of ${\mathrm{NbSe}}_{3}$ the broadband noise of the sliding charge-density wave (CDW) can be partially resolved into two-state and multistate fluctuators, which show strong sensitivity to the bias current and temperature. Explicit violations of detailed balance appear. Near the threshold bias for slid…
Fullerenes have been converted to diamond crystals with the size of 0.1 mm at 5.0–5.5 GPa and 1400 °C, using NiMnCo catalyst. They are similar to graphite in the growing phenomena. They are transformed into diamond directly without being graphitized first.